Large Eddy Simulation Of The Flowfield In A Supersonic Combustor With Cavity Flameholder

Taking the injection mixing and combustion flame stabilizer as mian research object,The typical flow field structure of supersonic combustion chamber were investigated through numerical simulation.Firstly,the simulation of single cavity combustion chamber under cold flow condition is carried out based on LES/RANS method,Which analyzes the influence of concave cavity configuration on the mixing characteristics of supersonic transverse jet,and demonstrates the development and evolution of typical structure Counter-Rotating Vortex Pair(CRVs)in the mainstream of Jet Wake,and focuses on two typical flow fields of jet cavity interaction: Medium Interaction flow field mode and strong interaction flow field mode.According to the simulation results,the development form of shear layer is the key factor to determine the interaction mode between jet and concave cavity.In the medium interaction mode,The shear layer at the rear of the jet near the side of the cavity enters the cavity and develops,which will form the wall Trailing Counter-Rotating Vortex Pair(TCRVs)and the CRVs as well as the new vortex to jointly dominate the three groups of Vortex forms;In the strong interaction flow field mode,The shear layer develops above the cavity and will form two groups of CRVs to lead the model together.Secondly,based on the hybrid LES/RANS method of chemical non-equilibrium flow,the combustion flow field and the characteristic structure of the flow field of the parallel posterior edge expansion cavity are investigated.Under the condition of cold flow,the jet position and jet injection pressure will apparently affect the vortex intensity and distribution in the cavity,even directly affect the characteristics of circumfluence in the cavity.Under combustion conditions,Because of its relatively low calorific value,the direct ignition of hydrocarbon fuel is easy and unsuccessful,while hydrogen is easy to ignite and easy to build a more stable combustion field.Then,the flame spreading process of ethylene after ignition in the front of the concave cavity is analyzed,and it is found that ethylene ignition has high requirements for ignition intensity,Which is difficult to form a larger combustion zone.The combustion flow field guided by hydrogen ignition can construct a strong reverse pressure zone and a larger cavity reflux zone.The combustion back pressure travels upstream along the subsonic region,causing the increasement of jet penetration depth,while the strength of the shock string increases and goes upstream,and a better flame stability condition is constructed.